在环境条件下进行的基于悬臂的原子力显微镜(AFM)已成为表征新材料系统和设备的重要工具。当前的仪器允许在大面积上进行强大的扫描,原子尺度横向分辨率,以及使用多频和多模态AFM操作模式对各种样品属性的表征。新型量子材料和器件的研究,然而,通常需要低温和超高真空(UHV)条件,更具体地说,AFM仪器提供原子分辨率。为此,基于音叉力传感器的AFM仪器变得越来越流行。与微制造悬臂相比,更宏观的音叉,然而,缺乏敏感性,这限制了测量带宽。此外,多模态和多频率技术,例如在环境条件下进行的基于悬臂的AFM中可用的那些,很难实施。在这篇文章中,我们描述了基于悬臂的低温UHVAFM设置,该设置允许将针对环境条件开发的通用AFM技术转移到UHV和低温条件。我们证明了这种基于悬臂的AFM通过允许具有优越的力导数灵敏度和带宽的多模态或多频率操作来提供实验灵活性。我们的仪器具有亚皮米间隙稳定性,不仅可以同时绘制具有原子尺度分辨率的垂直和横向力,但也执行快速概述扫描与尖端保持在更大的尖端样品距离的强大的成像。
Cantilever-based atomic force microscopy (AFM) performed under ambient conditions has become an important tool to characterize new material systems as well as devices. Current instruments permit robust scanning over large areas, atomic-scale lateral resolution, and the characterization of various sample properties using multifrequency and multimodal AFM operation modes. Research of new quantum materials and devices, however, often requires low temperatures and ultrahigh vacuum (UHV) conditions and, more specifically, AFM instrumentation providing atomic resolution. For this, AFM instrumentation based on a tuning fork force sensor became increasingly popular. In comparison to microfabricated cantilevers, the more macroscopic tuning forks, however, lack sensitivity, which limits the measurement bandwidth. Moreover, multimodal and multifrequency techniques, such as those available in cantilever-based AFM carried out under ambient conditions, are challenging to implement. In this article, we describe a cantilever-based low-temperature UHV AFM setup that allows one to transfer the versatile AFM techniques developed for ambient conditions to UHV and low-temperature conditions. We demonstrate that such a cantilever-based AFM offers experimental flexibility by permitting multimodal or multifrequency operations with superior force derivative sensitivities and bandwidths. Our instrument has a sub-picometer gap stability and can simultaneously map not only vertical and lateral forces with atomic-scale resolution, but also perform rapid overview scans with the tip kept at larger tip-sample distances for robust imaging.